Bluetooth® technology allows for, inter alia, wireless control of and communication between a mobile telephone and a headset/handsfree unit. A Bluetooth headset or earpiece allows a mobile phone user to have a telephone conversation without actually having to open or hold the mobile phone. Additionally, many mobile phones today have the capability to play stored or streamed audio and video, such as MP3 files, via the mobile phone speaker or the wireless headset. The streamed or stored media can likewise be communicated to a headset or earpiece using Bluetooth technology.
The Bluetooth audio output devices include their own batteries and are otherwise independent of the portable devices supplying the audio information to them. As a result, the battery life of a Bluetooth audio device has no correlation with the battery life of the mobile phone or other source of the audio stream. However, the rate of power consumption by the Bluetooth audio device is dependent upon the format of the audio being received and processed by it.
The Bluetooth protocol supports both asynchronous and synchronous communications. A synchronous link is referred to as a synchronous connection-oriented (SCO) link. An asynchronous link is referred to as an asynchronous connectionless (ACL) link. The Bluetooth Hands Free Profile (HF) uses the SCO link to carry a mono, pulse code modulated (PCM) audio channel. The Bluetooth Advanced Audio Distribution Profile (A2DP) defines the protocols and procedures for distributing high-quality audio content in mono or stereo on ACL channels.
The mobile phone and Bluetooth audio device each contain transmitter and receiver circuitry to communicate. The mobile phone transmits audio information to the Bluetooth device encoded in data packets. The quality of the audio communicated using the A2DP stereo format is considerably better than that of audio sent in the HF mode. Using the A2DP stereo format, more information defining the audio signal is encoded within the data packets transferred. Therefore, the audio information packets are longer in the A2DP mode.
The transmitter and/or receiver circuitry of both the mobile phone and the Bluetooth audio output device is turned off when it is not needed (e.g., between packets or when no information is scheduled for transmission) in order to conserve battery power. Because the packets for the A2DP stereo format are longer than the packets for the HF format, the transmitters of the mobile phones and the receivers of the Bluetooth audio output devices are on longer. Additionally, the processors and any decoding/encoding circuitry require more processing power to handle stereo A2DP packets than HF packets. Therefore, the stereo A2DP connection consumes significantly more battery power than does a mono HF connection.
For example, the Motorola HT820 stereo headphones support both listening to stereo music and conducting phone calls. Assuming the headphones' battery is fully charged, talk time for such headphones, when using the HF format, is approximately seventeen (17) hours, whereas, listening time, when using the A2DP stereo format for music, is reduced to only twelve (12) hours. In a second example, the Logitech HS210 headphones provide ten (10) hours of talk time, but only eight (8) hours of music time.
As evident from the foregoing examples, the battery life of a Bluetooth audio device is reduced at differing rates depending on how the wireless headset is used (talk vs. music), or which format (HF, A2DP mono, or A2DP stereo) is used. Additionally, if the battery level of the Bluetooth audio output device is low, continuing to use the A2DP stereo format instead of the HF mono format will decrease the battery level of the device at a faster rate.
Wireless phones and other media sourcing devices are typically equipped to automatically re-route the audio output in the event that the link to the Bluetooth device goes down or at least degrades below a pre-established threshold. For example, if the Bluetooth link dies while the user is in a phone call, listening to music, or in the middle of receiving a call indication, the audio is automatically re-routed to an alternate destination (usually back to the handset), so that the user can continue the current activity. Consider, for example, a user talking in a phone call using a Bluetooth headset. If the headset battery dies, resulting in Bluetooth link failure, the audio may be suddenly re-routed to the handset, presenting a situation that can be quite unexpected and confusing to the user. If the user does not realize what has happened quickly, he/she may think the call has been prematurely disconnected. Thus, audio re-routing responsive to Bluetooth link failure is a reactionary philosophy because no action takes place until after the problem has occurred. Nothing is presently done in anticipation of the Bluetooth audio device battery dying in order to prevent or at least mitigate user discontent.
Therefore, a need exists for a method for managing information signal distribution between communication devices (e.g., between a mobile phone and a Bluetooth audio output device) that proactively monitors operating characteristics of at least the hands-free device and takes preventive audio transmission or routing action to thereby overcome the shortcomings of the prior art.